LWD technology is the key signal transmission, roller reamers drilling it is currently widely used drilling fluid pressure pulse transmission, which is currently LWD tools commonly used method, which is to convert the measured parameters into the drilling fluid pressure pulse, with the drilling fluid circulation transferred to the ground. Its principle is shown briefly shown after the measured parameters by digitally encoded into high ("1") and low ("0"), the electrical signal, which controls the drilling fluid pulse generator mushroom head, when encoded as " 1 ", the shift mushroom head, so that drilling fluid flowing through the conical opening resistance increases, resulting in additional pressure. When encoded as "0", mushroom head down back in place, the pressure to normal. This is a positive pulse transmission system. There are similar negative pulse transmission systems, continuous-wave transmission system. Advantages drilling fluid pressure pulse propagation is economical, convenient, the disadvantage is the data transfer rate (the number of bits transmitted per second) is low. In recent years, in order to increase the transmission rate again try electromagnetic transmission technology, it is the LWD tools on the non-magnetic drill collar, between the non-magnetic drill collars and the upper pipe, there is a short section of insulation in order to contain low-frequency electromagnetic wave propagation information measured Mukai week the formation. On the ground, as a voltage difference between the rig and the ground electrode is detected. Early electromagnetic wave transmission because the signal attenuation, transmission distance is short and the high cost of commercial failure, due to technological drilling jars manufacturers improvements in recent years has begun to enter the market, the advantage is the transmission rate is not affected by fluid performance. In addition, underground storage, all data stored in underground storage, to be recovered from drilling data. The advantage is a low cost, reliable data storage. The disadvantage is that the ground can not get real-time data needed to guide drilling. For large amounts of data LWD, such as imaging logging while drilling, usually using real-time transmission and underground storage combination of approaches, key hole section using real-time transmission, while the other section with underground storage wells.